1. Field of the Invention
The invention relates to a sensor assembly for producing a signal representing the angular position of a selector disc about an axis.
2. Description of the Prior Art
The prior art discloses various sensor arrangements for determining the selector position, in particular of a transmission controller. For example, DE 199 29 632 A1 discloses an apparatus for registering the position of the movements of two axles, in particular the selector position of a transmission controller, in which at least one cam track is formed on a shaft, along which track an extension of a sensing lever slides. Movement of the extension is converted into an output signal with the aid of a sensor. In this case, as viewed in the axial direction of the shaft, on both sides of a first cam track having a surface running in a circle there are a second and a third cam track, these each having sections with a different design one behind the other, as viewed in the circumferential direction of the shaft. In this case, a sensing lever is pressed onto the outer face of the cam by a spring element, the lever having a spherical tip. Via this sensing lever, during the movement of the shaft in the axial direction and in the rotational direction, these two movements are continuously tracked by the sensing lever with its tip and, in this way, the selector position is determined. The disadvantage here is that the apparatus has a geometric track, which is difficult to fabricate. Since the shaft also executes a movement in the axial direction, the sensing lever has to be mounted in a complicated manner.
Furthermore, DE 199 20 440 A1 discloses a multi-step transmission for a motor vehicle having a plurality of wheel sets corresponding to a plurality of gears and having a rotatable selector drum which has at least one circumferential groove, in which an axially displaceable guide element is guided, and is coupled to means for engaging and disengaging at least one of the gears. In this case, a further rotatable selector drum is provided, having at least one further circumferential groove in which a further axially displaceable guide element is guided, and is coupled to means for engaging and disengaging at least one other of the gears. In this arrangement, the control and actuation for the selector drums can have a different configuration. For example, cam discs can be provided, which are connected to the selector drums with a force fit or form fit or are formed integrally. Here, the circumference of the cam discs can be provided with a larger radius in angular regions corresponding to the selector positions of one of the gears rather than in the angular regions corresponding to the neutral selector positions. The cam discs, in this case, comprise radially projecting angular regions, which correspond to the selector positions of the gears, and radially setback angular regions, which correspond to the neutral selector positions. In this arrangement, the very accurate and variable control and actuation of the respective selector position is likewise advantageous, but the disadvantage here is that this apparatus does not permit the selector position to be determined merely from the position of the cam disc.
EP 1 094 253 A2 discloses a selector arrangement having a control device in which the various shaft positions of the input and output shafts of a step-up transmission are registered by means of various sensor elements and are further processed by an electronic controller. In this case, the design of the arrangement is used in particular to reduce weight and to increase reliability.
DE 43 14 952 A1 discloses an apparatus for registering the gear position of a multi-step transmission whose transmission steps can be selected by a selector shaft, which is mounted such that it can be rotated about its axis and also displaced in the direction of its axis in a housing of the multi-step transmission using digital selector elements. In this case, a combination of digital and analog selector elements is provided, in such a way that digital selector elements are provided to register the aisles, and analog selector elements are provided to register the gears. The analog selector element can have different designs, for example, it can be designed as a rotational angle sensor or else as a travel sensor.
On the basis of these known sensor arrangements for determining the selector position, in particular of a transmission controller, this invention provides a sensor arrangement which has a simpler construction than the known sensor arrangements.
According to the invention, a running track has, at least to some extent, regions for gear positions, neutral positions and selector sections. A selector section is arranged between a gear position and a neutral position. The position data registered by the sensing device and belonging to gear positions and neutral positions is different from the position data belonging to the selector sections. The position data of the selector sections, which are directly adjacent to a gear position or a neutral position, are different from one another.
In this way, the possibility is provided for the sensor disc not only to detect the individual selector positions, viz., the gear positions G, the neutral positions N and any desired reference neutral step nN as a detent point, but also simultaneously, via the regions between the selector sections NG and GN, on the basis of the sensor position and the direction of rotation, to detect whether the next selector position is neutral or a gear. The combined registration of the position data via a single sensor disc, without axial displacement of sensing device or sensor disc, leads to a considerable simplification of the production of the sensor arrangement and makes it possible to use simpler sensor elements. Nevertheless, the arrangement makes it possible to determine the selector position and to monitor the selector drum.
In an advantageous refinement of the invention, the running track has a detent groove and at least one gear position or neutral position, and the sensing device is pressed onto the running track by means of a suitable element. The functionality of the sensor arrangement comprising the sensor disc and sensing system is therefore expanded by the function of a mechanical detent system, such as is used in a manual multi-step transmission. The sensing head interacting with the running track latches into the gear or neutral selector positions by pressing the sensing device onto the running track.
In a further inventive embodiment, the running track has variable position data in the region of a selector section. This can mean, for example, that the selector section is of ramp-like design with respect to the position data to be measured, by which means the position data can be assigned a unique position of the sensor disc. Individual selector sections can have the respectively identical variable position data, or else each selector section has its own singular position data. Any combination is also possible, for example, some of the selector sections can have the same course of the position data, and some others a different course of the position data.
The running track advantageously has different position data between the selector positions of gear positions and the selector positions of neutral positions. It is therefore possible to detect immediately whether a gear is selected or whether the transmission is in neutral.
Furthermore, the running track can have different position data at least for individual gear positions. The gear engaged can therefore be determined immediately from the position data.
Furthermore, the running track can have different position data at least for individual neutral positions. Therefore, the gears, between which the selector drum is in neutral, can be determined immediately from the position data. This is necessary in particular for a reference neutral. There is a reference neutral position, for example between a forward gear and a reverse gear, which has its own position data enabling immediate detection. One use for this is the neutral position of the transmission, for example when starting a motor, when no selection has yet been made. The first selection is then carried out from this position.
In a preferred embodiment, the sensor disc has different diameters along its running track in order to produce different position data in the radial direction. This corresponds to a running track arranged in the circumference of the sensor disc, which is sensed predominantly in the radial direction by the sensing device. The circumferential changes are registered as position data and can be assigned appropriately to the sensor disc position.
In a further embodiment, the sensor disc has a running track which, as viewed in the axial direction of the sensor disc axis, is not flat, in order to produce different position data in the axial direction. This corresponds to an arrangement of the sensing device in the axial direction. The sensing system registers the axial unevenness at the end of the sensor disc and assigns this position data to a sensor disc position. Of course, a combination of axial position data determination and radial position data determination, as described in the previous paragraph, is also possible. However, at least two sensing devices are then expediently used.
In a further preferred embodiment, the sensing device has a rotatably mounted ball in order to sense the running track of the sensor disc. The ball, as a sensing head, reduces friction between the sensing device and running track, which permits reliable selection and accurate measurement in the region of the detent grooves. In principle, however, the sensing device can have any known sensing head for sensing surfaces, and is therefore not restricted to a ball as sensing head.
The sensing device preferably has a sensor designed as a Hall element. As a result, movement of the sensing device resulting from the change in the position data can be used to determine the relative displacement and therefore the position data very accurately. In the case of the sensor designed as a Hall element, it is primarily a linear displacement of the sensing device that is measured. Any other displacement or rotation of the sensing device can also be used to determine the position data and can be registered by means of suitable sensors.